The present invention relates to methods for treating a subterranean formation. More particularly, the present invention relates to methods of using water-soluble hydrophobically modified polymers to treat intervals of a subterranean formation having variable permeabilities.
In subterranean treatments, it is often desired to treat an interval of a subterranean formation having sections of non-uniform permeability. However, due to the interval's variable permeability, it may be difficult to obtain a uniform distribution of the treatment fluid throughout the entire interval. For instance, the treatment fluid may preferentially enter portions of the interval with high permeability at the expense of portions of the interval with lesser permeability. In some instances, these intervals with variable permeability may be water-producing intervals. In other instances, these intervals with variable permeability may be weakly consolidated intervals. As used in this disclosure, the phrase “weakly consolidated interval” includes one or more portions of a subterranean formation that contain loose particulates and particulates bonded with insufficient bond strength to withstand the forces created by the production (or injection) of fluids through the formation. These particulates may include, among other things, sand, gravel, fines and/or proppant in the subterranean formation, for example, proppant placed in the subterranean formation in the course of a fracturing or gravel-packing operation. A weakly consolidated interval may include fractures in the formation wherein weakly consolidated particulates reside within the open space of the fracture, e.g., a proppant pack.
In an attempt to facilitate the uniform distribution of treatment fluids throughout the entire interval, a variety of techniques have been used to divert treatment fluids to less permeable portions of the interval. Such techniques have involved, among other things, the injection of particulates, foams, or blocking polymers (e.g., crosslinked aqueous gels) into the interval so as to plug off the high-permeability portions of the subterranean formation, thereby diverting subsequently injected fluids to less permeable portions of the subterranean formation. While each of these diversion techniques has been used successfully, there may be disadvantages. In some instances, plugging off the high-permeability sections may not be suitable for a producing interval, for example, because the injected solution (or material) may reduce or stop the flow of hydrocarbons in addition to the achieving a desired diversion of the treatment fluid. Therefore, to return the interval to production, expensive and/or time-consuming remedial treatments may be required to remove the injected solutions (or materials). Furthermore, techniques geared toward injecting solutions (or materials) designed to plug off high-permeability intervals of the formation may require expensive zonal isolation, which may be inaccurate, leading to inadvertent plugging of and/or damage to the hydrocarbon-bearing sections.